1. Field of the Invention
The present invention relates to thickened latex compositions and, more particularly, thickened latex paint compositions.
2. Description of the Prior Art
Water-based latex paints and coatings (latex compositions) are widely used in industrial and residential applications. In order to perform properly, these latex compositions must be able to be applied uniformly to horizontal (top and bottom), vertical, and even intricately shaped objects with a minimum tendency to run. Such performance requires rheology control during and after application of the latex compositions. Typically, latex compositions can be applied by one of several methods, including spraying, brushing or applying by means of a roller. Accordingly, rheology control of the compositions must be such as to allow alternate methods of application. Additionally, since the formulations are all suspensions of solids, e.g., pigments, in liquid, the rheology must be controlled during production as well as during storage to prevent undue settling and separation of the components of the formulation.
It is well known that organic thickeners such as hydroxyethyl cellulose (HEC) can be used to thicken water-based latex compositions. Additionally, certain clays that are known to act as thixotropes in water solutions are also used, alone or in conjunction with HEC, as thickening agents. More recently, there have been developed what are known as "Associative Thickeners," which are generally synthetic polymeric materials dispersed in water-compatible (-miscible) liquids.
It is well known that monohydrated aluminas, e.g., boehmite aluminas, can be used as thickeners for simple aqueous solutions. For example, the prior art discloses the use of such boehmite aluminas as thickeners in aqueous cleaning formulations.